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Tuareg Shield
The Tuareg Shield is a geological formation lying between the West African craton and the Saharan Metacraton in West Africa. Named after the Tuareg people, it has complex a geology, reflecting the collision between these cratons and later events. The landmass covers parts of Algeria, Niger and Mali. Origins The Tuareg Shield is mainly composed of Archean or Paleoproterozoic terranes and Neoproterozoic terranes that amalgamated during the Pan African orogeny when the West African craton and the Saharan metacraton converged. The shield originated in oceanic island arcs that formed on the cratons during 900 Ma to 680 Ma, of which relics remain as thrust sheets on top of more rigid bodies. In Mali, the Tilemsi belt is a complex of intraoceanic arcs that formed above a subduction zone sloping down to the east and were accreted to the shield during the Pan-African orogeny. The western part of the Hoggar Mountains (Ahaggar Mountains) is made of material from the Pharusian Ocean. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West African Craton
The West African Craton (WAC) is one of the five cratons of the Precambrian basement rock of Africa that make up the African Plate, the others being the Kalahari craton, Congo craton, Saharan Metacraton and Tanzania Craton.Jessell M.W., Liégeois J-P. (2015). "100 years of research on the West African Craton". ''Journal of African Earth Sciences''. 112(B): 377– 381. Cratons themselves are tectonically inactive, but can occur near active margins,Ennih N. & Liégeois J-P. (2008). ''The Boundaries of the West African Craton''. Geological Society, London, Special Publications. 297: 1–17. with the WAC extending across 14 countries in Western Africa, coming together in the late Precambrian and early Palaeozoic eras to form the African continent. It consists of two Archean centers juxtaposed against multiple Paleoproterozoic domains made of greenstone belts, sedimentary basins, regional granitoid-tonalite-trondhjemite-granodiorite, tonalite-trondhjemite-granodiorite (TTG) plutons, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tilemsi Belt
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Tilemsi may refer to two communes in Mali: *Tilemsi, Gao *Tilemsi, Tombouctou Tilemsi is a commune of the Cercle of Goundam in the Tombouctou Region of Mali Mali (; ), officially the Republic of Mali,, , ff, 𞤈𞤫𞤲𞥆𞤣𞤢𞥄𞤲𞤣𞤭 𞤃𞤢𞥄𞤤𞤭, Renndaandi Maali, italics=no, ar, جمهو ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Historical Geology
Historical geology or palaeogeology is a discipline that uses the principles and methods of geology to reconstruct the geological history of Earth. Historical geology examines the vastness of geologic time, measured in billions of years, and investigates changes in the Earth, gradual and sudden, over this deep time. It focuses on geological processes, such as plate tectonics, that have changed the Earth's surface and subsurface over time and the use of methods including stratigraphy, structural geology, paleontology, and sedimentology to tell the sequence of these events. It also focuses on the evolution of life during different time periods in the geologic time scale. Historical development During the 17th century, Nicolas Steno was the first to observe and propose a number of basic principles of historical geology, including three key stratigraphic principles: the law of superposition, the principle of original horizontality, and the principle of lateral continuity. 18th-century ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geology Of Africa
The geology of Africa is varied and complex, and gives rise to the wide variety of landscapes found across the continent. The African continent rests over two main plates. The African plate, accounting for the whole of north Africa, and the Somali plate, which accounts for the eastern side of mid and southern Africa. The Somali plate is moving away from the African plate in a split from Djibouti in the north, to Eswatini in the south. The parting of these two plates formed the southern part of what used to be known as The Great Rift Valley. In geological terms, the African and Somali plate separation has formed the East African Rift System (EARS), comprising two separate rifts systems - the Eastern Rift Valley, and a western branch known as the Albertine Rift. Two massive domes were formed, the Kenyan dome and the Ethiopian dome (known as the Ethiopian Highlands). The Albertine Rift follows the western edge of the Kenyan dome. This runs from Lake Malawi in the south, up into Lake ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga) to the beginning of the Cambrian Period, about million years ago ( Ma), when hard-shelled creatures first appeared in abundance. Overview Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered from the 1960s onwards. The Precambrian fossil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mediterranean
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the east by the Levant. The Sea has played a central role in the history of Western civilization. Geological evidence indicates that around 5.9 million years ago, the Mediterranean was cut off from the Atlantic and was partly or completely desiccated over a period of some 600,000 years during the Messinian salinity crisis before being refilled by the Zanclean flood about 5.3 million years ago. The Mediterranean Sea covers an area of about , representing 0.7% of the global ocean surface, but its connection to the Atlantic via the Strait of Gibraltar—the narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates the Iberian Peninsula in Europe from Morocco in Africa—is only wide. The Mediterranean Sea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Celtic Britons, Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same Rock (geology), rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed Stratum, strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Union of Geological Sciences, Intern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phanerozoic
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the '' Precambrian'', is now divided into the Hadean, Archaean and Proterozoic eons. The time span of the Phanerozoic starts with the sudden appearance of fossilised evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the emergence and development of complex plants; the evolution of fish; the emergence of insects and tetrapods; and the development of modern fauna. Plant life on land appeared in the early Phanerozoic eon. During this time span, tectonic forces which move the continents had collected them into a single landmass known as Pangaea (the most recent supercontinent), which then separated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orogenic
Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent boundary, convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is tectonic uplift, uplifted to form one or more mountain ranges. This involves a series of geological processes collectively called orogenesis. These include both structural deformation (physics), deformation of existing continental crust and the creation of new continental crust through volcanism. Magma rising in the orogen carries less dense material upwards while leaving more dense material behind, resulting in compositional differentiation of Earth's lithosphere (crust (geology), crust and uppermost mantle (geology), mantle). A synorogenic process or event is one that occurs during an orogeny. The word "orogeny" () comes from Ancient Greek (, , + , , ). Although it was used before him, the term was employed by the American geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aïr Mountains
The Aïr Mountains or Aïr Massif ( tmh, Ayăr; Hausa: Eastern ''Azbin'', Western ''Abzin'') is a triangular massif, located in northern Niger, within the Sahara. Part of the West Saharan montane xeric woodlands ecoregion, they rise to more than and extend over . Lying in the midst of desert north of the 17th parallel, the Aïr plateau, with an average altitude between , forms an island of Sahel climate which supports a wide variety of life, many pastoral and farming communities, and dramatic geological and archaeological sites. There are notable archaeological excavations in the region that illustrate the prehistoric past of this region. The endangered African wild dog (''Lycaon pictus'') once existed in this region, but may now be extirpated due to human population pressures in this region. Geology The Precambrian to Cenozoic Aïr Mountains consist of peralkaline granite intrusions which appear dark in colour (unusual since most granitic masses are light-ton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adrar Des Ifoghas
The Adrar des Ifoghas (also Adrar des Iforas; Tamasheq: ⴰⴷⵔⴰⵔ ⵏ ⵉⴼⵓⵖⴰⵙ in Tifinagh; Adrar n Ifoghas; ar, أدرار إيفوغاس Ifoghas' Mountains) is a massif located in the Kidal Region of Mali, reaching into Algeria. It has an area of around 250,000 square kilometers (97,000 square miles). Geography The Adrar des Ifoghas area is characterized by wide, shallow valleys and is strewn with piles of eroded granite blocks. The massif's valleys open to the Tamesna plain on the east, to the Telemsi fosse on the west, to the western basin of the Azaouak valley on the south and to the Tanezrouft on the north. Settlements of the area include Kidal, Aguel'hoc, Boghassa, Essouk and Tessalit. The Adrar des Ifoghas is known locally as "Adagh". "Adrar" is the Berber word for mountain, while "Ifogha" is the name of an aristocratic Tuareg clan, "Kel Ifoghas", who have dominated the region for generations. Like most Tuareg, the Kel Ifoghas are nomadic, raising cam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pharusian Ocean
The Pharusian Ocean is an ancient ocean that existed from 800 to 635 million years ago, between the break-up of the Rodinia supercontinent and the start of formation of the Gondwana supercontinent. Opening and closure The Pharusian Ocean opened around 800 million years ago in the Neoproterozoic era after rifting along the eastern margin of the West African craton during the breakup of Rodinia. The ocean began to close around 730 million years ago with eastward subduction of the Tilemsi arc, which was accreted against the Hoggar region of the Saharan Metacraton. The western part of the Hoggar massif is made of material from the Pharusian Ocean including oceanic basalts, arc volcanic and sedimentary rocks and sediments that were shed into the Pharusian Ocean by the West African craton and the eastern Hoggar. Closure was completed when the West African and Saharan cratons collided around 635 million years ago at the start of the Pan-African orogeny. Southern extension The Goiás Oce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
